1. Field of the Invention
The present invention relates to a particle sensor of the type used in particular in the detectors of particle physics research installations such as particle accelerators, collision apparatus and the like. A sensor of this type is intended in particular to locate accurately the point of passage and of interaction of particles generated during experiments conducted in such apparatus.
2. Description of the Prior Art
A sensor of the above type is described in an article by P. Weiss et al., presented at the 7th International Conference on Solid State Actuators and Detectors under the title xe2x80x9cWafer-scale Technology For Double-sided Silicon Microstrip Particle Detectorsxe2x80x9d.
The above prior art detector is essentially designed to analyze high-energy particles but it is ill-suited to detecting particles having a low energy, such as xcex1 particles or protons, because it is optimized for particles having a very long range.
The object of the invention is to provide a particle sensor enabling sensing of low-energy particles.
The invention therefore provides a particle sensor, in particular for a detector for analyzing products of collisions in particle physics apparatus, comprising:
a semiconductor substrate,
a plurality of doped regions formed in said substrate and each forming a diode in conjunction with said substrate,
means for defining on top of a first face of said substrate a plurality of current collection areas for respectively collecting currents circulating in each of said diode regions as the result of impacts of particles on said sensor, said means for defining said current collection areas being adapted to be connected to means for using signals formed by the collected currents,
biasing means for biasing each of said diode regions and for bringing said substrate to a totally depleted state, and
means for defining on said first face of said substrate a plurality of particle detection areas each of which is contiguous with a respective current collection area, said means for defining said detection areas having a thickness on top of said substrate which is less than that of said means for defining said current collection areas to enable detection of low-energy particles.
Because of the above features, the sensor has separate areas specifically dedicated to collecting current and detecting particles. The detection areas can therefore have the minimum thickness and do not impede the passage of particles into the substrate.
According to other advantageous features of the invention:
the current collection areas and the detection areas have an elongate shape and are disposed in an alternating arrangement parallel to an edge of the substrate;
the current collection areas surround the detection areas and form respective areas disposed in a matrix on the first face of the substrate;
the means for defining a detection area comprise an oxide layer deposited on the first face of the substrate;
the oxide layer is covered with a thin protective metalization layer;
the face of the substrate opposite the first face comprises a current collecting device;
the thickness of the oxide layer is less than or equal to 50 nm;
the thickness of the protection layer is less than or equal to 40 nm;
the width of a detection area is greater than or equal to that of a current collection area.
Other features and advantages of the invention will become apparent during the course of the following description, which is given by way of example only and with reference to the accompanying drawings.